1 - Across the army, 'Nids do not have Acute Senses. They just haven't consumed enough space wolves...

2- INAT FAQ page 103

'TYR.41E.01 – Q: Is the „Pheromone Trail‟ Reserves roll bonus cumulative if you have more than one Lictor (including Deathleaper)?
A: No, you only get +1 to your Reserve rolls no matter how many Lictors (including Deathleaper) you have on the table [clarification].
Ref: TYR.34B.02'